Yes, you can do it. Using the move paper menu command on the control panel, it is certainly possible. You have the issue of how easy it is going to be to evaluate the proofs while still on the printer, and the possibility of some paper transport issues if you are printing on a delicate surface. I sometimes do this with canvas. You will need to trick the printer by choosing a larger paper size to allow you to accurately position the test prints, since by default page sizes are placed to the right side of a roll. Choose a page size that is the full width of the roll for the proof and place it on the right side of the page in Photoshop's print dialogue to get it to print on the left side of the roll (the prints come out top first from the printer). You can then use a normal page size for the full size images and it will print on the right side of the roll as it exits the printer. It may be more straightforward if you are using Qimage. Another approach would be to print the proofs, then slice them off of the roll and feed the remainder as larger sheets instead of a roll.
